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Amateur Seismic Network - 1941 Tsunami
Detection of the 1941 Tsunami in Sri Lanka Amateur Seismic Networkhttp://asc-india.org/menu/ The Tsunami of 1941 following an earthquake in the Bay of Bengal was detected in Sri Lanka. It was reported on as follows1941: " Andaman Islands, India, Mw 7.7 Date : 26th June 1941 Epicentre: 20.5 kilometres W of Flat Island India Latitude: 12.500 N (5) Longitude: 92.570 E (5) Origin Time: 11:52:03 UTC (5) Magnitude: Mw 7.71 (3), Mb 8.0 (4), Ms 7.7 (4) Moment: 4.25*10*20 Nm (3) " The earthquake of June 26, 1941 is among the strongest earthquakes ever recorded in the Andaman & Nicobar Islands. It had a magnitude of 7.7 (Mw).It was centred (5) in the Bay of Bengal, roughly, 20.5 kilometres W of Flat Island, India or 23.6 kilometres WNW of Yadita (Middle Andaman Isl.), India,or 96.7 kilometres NNW of Port Blair (South Andaman Island), India,or 617 kilometres SW of Yangon, Myanmar,or 834 kilometres NNW of Banda Aceh (Sumatera), Indonesia. It was the last great earthquake in the Andaman and Nicobar Islands. The 1881 Nicobar Islands earthquake (M7.9) is the only other event of comparable magnitude. This 1941 earthquake caused widespread damage on Middle and South Andaman Islands. Most masonry structures in and around Port Blair were badly affected. The Cellular Jail which was a 3 storey building with 696 solitary cells and infamous for the imprisonment, torture and murder or freedom fighters, including Vinayak D. Savarkar was destroyed as were all the elegant buildings and wide roads, on Ross Island, the administrative centre of the British. The maximum intensity (4) was experienced at Baratang Island, Shoal Bay creek, north of Port Blair and near Port Anson.Tremors from the earthquake were felt (6) in cities along the Coromandel (eastern) coast of India and even in Colombo, Sri Lanka. In Madras (now Chennai), two tremors were felt, the first of 2 seconds and the second lasting 15 seconds. It was felt throughout the city, mostly by people in tall buildings. At some locations, doors and windows are reported to have "slammed with a bang" and "chairs rocked". Articles kept on shelves also fell onto the floor. The tremors in the city were reported to have been the strongest since 1899. At Vishakhapatnam, two shocks were experienced within two minutes. People went outdoors on feeling the tremors, as did employees at the Municipal buildings in the city, as they felt the buildings rocking. People outdoors are said to have had an "unusual experience". Tremors were also experienced at Calcutta (now Kolkata), Chandernagar and Cuttack. Shaking was felt for a duration of 4 minutes at Cuttack. Tremors were felt in Colombo, Sri Lanka for a few seconds and also at Syhlet, Bangladesh, where the Car Festival was suspended due to the quake. There are no reports of tremors being felt from Sumatera, Indonesia in June 1941. The earthquake was followed by several powerful aftershocks (5). Two magnitude 6.0 events struck within 24 hours of the main shock on June 27th, 1941. The first occurred at 07:32:47 UTC and was followed by another at 08:32:19 UTC. These were then followed by 14 earthquakes of magnitude 6.0 upto January 1942. A tsunami (1) was triggered by this earthquake in the Bay of Bengal. As per journalistic sources, the height of the tsunami was of the order of 0.75 to 1.25 meters. At the time no tidal gauge was in operation. Mathematical calculations suggest that the height could be of the order of 1.0 meter. This tsunami was witnessed along the eastern coast of India. It is believed that nearly 5,000 people were killed by the tsunami on the east coast of India. Local newspaper are believed to have mistaken the deaths and damage to a storm surge, however, a search of meteorological records (2) does not show any storm surge on that day on the Coromandel Coast. National dailies like the Times of India (6), which reported the quake's shaking effects did not mention any deaths, either as a result of a storm surge or a tsunami. REFERENCES :1) International Tsunami Symposium. :2) Murty, T.S., "Storm surges - meteorological ocean tides", Bulletin of the Fisheries Research Board of Canada, Ottawa, 1984. :3) Pacheco, Javier F., and Sykes, Lynn R., "Seismic moment catalog of large shallow earthquakes, 1900 to 1989", Bulletin of the Seismological Society of America, v. 82, no. 3, p. 1306 - 1349, 1992. :4) Dasgupta, S., Pande, P., Ganguly, D., Iqbal, Z, Sanyal, K, Venkatraman, N.V., Dasgupta, S., Sural, B., Harendranath, L., Mazumdar, K., Sanyal, S., Roy, K., Das, L.K., Misra, P.S., Gupta, H., "Seismotectonic Atlas of India and its Environs", Geological Survey of India, 2000. :5) Tandon, A.N., and Srivastava, H.N., "Earthquake occurrence in India: Earthquake Engineering", Sarita Prakashan, Jai Krishna Vol., 1-48, Meerut, 1974. :6) Times of India newspaper archives (Mumbai), India ................................